The invention relates to a blade for a turbomachine, an integrally bladed rotor base body, as well as a turbomachine.
This type of blade for a turbomachine is disclosed, for example, in German Patent Application DE 10 2009 007 468 A1. It has a blade root, a blade neck, a blade pan and a platform configured between the blade neck and the blade pan, the platform having a front projection and a rear projection, as viewed in the flow direction of a hot gas flow, for the radially inner limiting of an annular space through which a hot gas flow streams and thus for delimiting a cooling air flow from the hot gas flow. Configured in the blade root is a cooling channel extending in the flow direction, via which the cooling air is guided in an internal blade pan cooling air system. For the purposeful guidance of the cooling air in the cooling air system, the cooling channel is sealed on its downstream outlet by a sealing element in the axial direction or at least the cross section is reduced. Even though this produces good cooling of the blade per se, the cooling air flow is strongly diverted or influenced. In addition, the blade roots are configured such that a passage is respectively formed between them, which is limited toward the annular space by laterally touching platform surfaces and through which the cooling air is able to flow from the high-pressure side to the low-pressure side. However, the passage may also be at least reduced in terms of cross section by the sealing element downstream from the blades. In order to prevent a gas exchange between the hot gas flow and the cooling air flow through the laterally touching platform surfaces, a seal is disposed between the same. In the event of damage to the seal, however, a considerable gas exchange may occur.
The object of the invention is creating a blade for a turbomachine in which the foregoing disadvantages are eliminated and in which an optimized cooling is made possible with an at least almost unimpeded flow-through of cooling air and with a structural delimiting of the hot gas flow from the cooling air flow. Furthermore, the object of the present invention is creating an integrally bladed rotor as well as a turbomachine.
A blade according to the invention for a turbomachine has a blade root, a blade neck, a blade pan and a platform configured between the blade neck and the blade pan, the platform having a front projection and a rear projection, as viewed in the flow direction of a hot gas flow, for delimiting a cooling air flow from the hot gas flow. According to the invention, the blade has at least one cooling channel for guiding at least one cooling air partial flow through the blade neck, whose inlet is disposed in the region of the front projection and whose outlet is disposed in the region of the rear projection.
Because of the at least one cooling channel on the blade-neck side, an unimpeded flow-through of at least one cooling air partial flow is able to take place, thereby achieving a high level of cooling of the blade in the neck region. In addition, the guidance of at least this cooling air partial flow is structurally separated from the guidance of the hot gas flow, which considerably hinders an undesired gas exchange. In particular, heat-conducting cross sections of the blade neck are reduced and heat-dissipating surfaces of the blade neck are increased, whereby a greater temperature gradient can be adjusted between a cold rotor hub and the hot blade pan. Load-bearing cross sections of the blade pan are put further outward in the circumferential direction, thereby making the blade pan stiffer and making it possible to design the blade neck with a reduced mass. Mass is hereby removed from the bending line, which also has a beneficial effect on the vibration behavior and running behavior of the blade. The at least one cooling channel may already be integrated during blade production or else afterward, for example, by means of electro-chemical processing such as ECM or PECM. Moving components for cooling the blade neck as well as attachment parts such as deflector plates and the like are not required. In addition, the cooling of the blade neck according to the invention may be combined with an internal blade pan cooling. It is expressly noted that these types of blades are suited both for integral attachment to a rotor hub or a base body of a rotor to produce an integrally bladed rotor base body as well as for detachable mounting on a base body of a rotor.
In the case of a preferred exemplary embodiment, the at least one cooling channel has a section with an expanded cross section between the inlet and the outlet. This creates a large volume cavity in the blade neck, thereby achieving a further increase in the heat-dissipating surfaces and appreciably reducing the wall thicknesses of the blade neck, which impedes the storage of heat. In addition, the weight of the blade is reduced.
In the case of one exemplary embodiment, at least one turbulator for vortexing the cooling air partial flow is disposed in the at least one cooling channel, thereby effecting an improved heat transfer from the heated blade neck walls to the cooling air partial flow.
However, so as not to withdraw too much kinetic energy from the cooling air partial flow and thereby weaken the cooling of the subsequent rows of blades, it is advantageous if the at least one turbulator is essentially located outside of or next to a fictitious channel axis extending between the inlet and the outlet.
The inflow as well as outflow of at least one cooling air partial flow can be improved in that the inlet and the outlet are aligned such that a swirl of the cooling air flow is utilized. Alternatively, the inlet and the outlet may also be aligned such that the swirl of the cooling air flow is prevented. In addition, the at least one cooling air partial flow may be improved by so-called “pumping,” which is achieved in that the channel axis is pointed diagonally outwardly. In other words, the outlet is disposed radially outwardly and the inlet is disposed radially inwardly.
To improve the structural mechanics, it is advantageous, as in one exemplary embodiment, if the at least one cooling channel is aligned according to the blade pan.
In order to guide as much cooling air as possible through the blade neck, one exemplary embodiment has a plurality of cooling channels, for example three channels. The cooling channels are preferably disposed next to each other in the transverse direction of the blade neck and may be separated from each other merely by relatively thin channel walls. The sum of their inlet widths corresponds hereby approximately to the width of the blade neck so that the blade neck in principle has no front-side staunching surfaces against which the cooling air flow could collide.
In order to cool the blade root, the blade root may have two concave side walls. A passage is hereby formed between two adjacent blade roots, through which a cooling air partial flow may also flow.
In order to prevent a gas exchange in the radial direction between the cooling air flow and the hot gas flow in the region of the platforms, in the case of one exemplary embodiment, an insertion groove for accommodating a sealing element is configured in each of the side walls of the blade neck.
A rotor base body according to the invention for a turbomachine has a plurality of blades according to the invention. Because of the reduced heat-transmitting cross sections and the increased heat-dissipating surfaces, the blades enable an adjustment of a sharp temperature gradient between the cold rotor hub and the hot blade pans, thereby allowing a disk or ring geometry that is far to the outside and achieving a reduction in the temperature in critical component regions.
In the case of one exemplary embodiment, the rotor base body is configured in a bling design (bladed ring) or a blisk design (bladed disk) as an integrally bladed rotor base body with integrally attached blades.
In the case of another exemplary embodiment, the rotor base body is provided with detachably mounted blades as a rotor base body.
A turbomachine according to the invention has a rotor with at least one integrally bladed rotor base body according to the invention. Because of the weight-reduced blades, this type of turbomachine has an improved running behavior and a lower fuel consumption.
Other advantageous exemplary embodiments of the invention are the subject of additional dependent claims.
A preferred exemplary embodiment of the invention will be explained in greater detail in the following on the basis of schematic representations.